Minnesota, feds play hot potato with hidden wall holding up St. Anthony Falls

Scientists are in the middle of inspecting — for the first time in decades — an unseen but critical piece of infrastructure holding up St. Anthony Falls in downtown Minneapolis.

But as that project nears completion, the federal government and the state of Minnesota have exchanged the first volley of disavowals, each saying a neglected “cutoff wall” beneath the falls isn’t theirs — and neither is the cost for any repairs that might arise from the inspection.

That 150-year-old wall has literally kept St. Anthony Falls from disintegrating. Were it to fail, the resulting flood would be disastrous.

This summer the Army Corps of Engineers released a draft disposition study for the Upper St. Anthony Lock and Dam, which the feds have been trying to unload ever since the lock closed to barge traffic a decade ago as part of an effort to stop the spread of invasive carp. (No one’s taken up the Corps’ offer to assume responsibility for a whole lock and dam.)

But buried in that study was a declaration about the cutoff wall that has been rankling Minnesotan environmental organizations and the Department of Natural Resources (DNR):

“USACE constructed a cutoff wall in the channel [of the Upper Mississippi River] between 1874 and 1876 to stabilize the Upper St. Anthony waterfalls,” according to the federal study. “The channel remains the property of the State of Minnesota; therefore, any maintenance of the cutoff wall is subject to state appropriations.”

Colleen O’Connor Toberman, land use and planning program director of Friends of the Mississippi River, said she was taken aback by the Corps’ assertion that the wall was Minnesota’s headache just because they built it in state waters.

The DNR’s official response conveyed the state’s surprise, before “unequivocally” denying ownership of the wall.

“USACE cannot legally construct a navigational project and then unilaterally decide that the State has ongoing responsibility for that project,” wrote DNR Assistant Commissioner Jess Richards.

He argued it wasn’t until 1925 that Minnesota created state agencies to actively engage in regulating public waters, so the state couldn’t have authorized the cutoff wall except by special legislation. And there’s no evidence of that, Richards wrote.

This “orphaned” piece of infrastructure, as legislators have been calling the cutoff wall, was built by the Army Corps of Engineers around 1875 as part of emergency efforts to stop the total collapse of the only waterfall on the Mississippi River. The cutoff wall is made of concrete. It’s over 1,800 feet long and ranges about 4 to 6½ feet thick. It starts under the riverbed and extends down into the highly erodible sandstone about 40 feet, just upstream from the crest of the falls above the Stone Arch Bridge.

In the 19th century, the milling industry central to Minneapolis’ creation story nearly destroyed St. Anthony Falls. Private power companies blasted myriad tunnels into the falls’ limestone banks to harness its hydropower for milling, and the botched construction of one of those tunnels triggered sudden and rapid erosion. The wall was a dramatic intervention built to stabilize the waterfall.

The cutoff wall helps maintain the Minneapolis water supply. If it failed, river levels could drop too low for the city to take in water, said Rep. Sydney Jordan, DFL-Minneapolis, who carried a bill, approved in 2023, to allocate $750,000 to the University of Minnesota to study the condition of the wall.

Minneapolis provides water to over a dozen cities — including hospitals and an international airport. It maintains a three-day drinking water reserve, said city spokesperson Allen Henry.

“The idea that it is an orphan project, everyone’s going to say it’s not mine, so we’re just going to ignore it, leaves our state at a tremendous risk,” Rep. Ginny Klevorn, DFL-Plymouth, said in a 2023 committee hearing.

Republicans ultimately supported the study as well, but were concerned funding the inspection might make the state appear to be assuming responsibility for any repairs that may come from it.

“We can’t do this on our own if we don’t actually understand who owns it,” said Rep. Jim Nash, R-Waconia, at the time. “We could assess the problem, but if we’re not, on our own, able to fix the problem, then I just feel like the state shouldn’t have to pay. ... If no other outside force acts on it, we’re going to have to come back and say well, we have to do it because we paid for the study.”

Last year, the inspection team started researching historical records on the wall and launched a geophysical investigation, using a ground penetrating radar device to survey the wall without physically seeing it. However, spring flooding kept water levels so high that the team had to pause their work and request a one-year extension from the legislature.

Field work has not resumed this summer, confirmed Bridget Mendel, spokesperson for the St. Anthony Falls Laboratory.

“They continue to have meetings with the project team and continue to plan for future steps, but there hasn’t been any physical work happening out there,” Mendel said. “It’s slow going. ... Since we have that extension, I think they’re working it into their schedule.”

The inspection report is due to the Legislature by July 1, 2026.

The scientists plan to eventually build a scale model of St. Anthony Falls to simulate what would happen if critical infrastructure at the site failed. Their findings would inform Hennepin County Emergency Management’s creation of a risk assessment.